import java.util.Iterator;

// 能够动态调整数组大小的实现
public class Stack_by_array<Item> implements Iterable<Item>{

    private Item[] a = (Item[]) new Object[1];
    private int N = 0;
    public boolean isEmpty(){
        return N == 0;
    }
    public int size(){
        return N;
    }
    private void resize(int max){
        // 将栈移动到一个大小为max的新数组
        Item[] temp = (Item[]) new Object[max];
        for (int i = 0; i < N; i++){
            temp[i] = a[i];
        }
        a = temp;
    }
    public void push(Item item){
        // 将元素添加到栈顶
        if (N == a.length) resize(2 * a.length);
        a[N++] = item;
    }
    public Item pop(){
        // 从栈顶删除元素
        Item item = a[--N];
        a[N] = null;
        if (N > 0 && N == a.length / 4) resize(a.length / 2);
        return item;
    }

    @Override
    public Iterator<Item> iterator() {
        return new ReverseArrayIterator();
    }
    private class ReverseArrayIterator implements Iterator<Item>{
        // 支持后进先出的迭代
        private int i = N;

        @Override
        public boolean hasNext() {
            return i > 0;
        }

        @Override
        public Item next() {
            return a[--i];
        }

        @Override
        public void remove() {

        }
    }

    public static void main(String args[]){
        Stack_by_array<String> s = new Stack_by_array<>();
        String[] strings = {"to", "be", "or", "not", "to", "-", "be", "-", "-", "that", "-", "-", "-", "is"};
        for (String a : strings){
            if (!a.equals("-")){
                s.push(a);
            }else if(!s.isEmpty()){
                System.out.println(s.pop()+" ");
            }
        }
        System.out.println("(" + s.size() + " left on Stack )");
    }
}
